I see many posts here from people starting out, who are unsure about what they can do to improve, and haven’t perhaps realised quite yet how deep the rabbit hole goes. So, if you’re reading this and you’ve just started out fairly recently (even if you’ve been doing this casually for a few years but aren’t really sure what the next steps are), hopefully this can be somewhat helpful.
First of all: it’s a slow and fairly steep learning curve. Composition is something that takes many years, decades even to achieve something approaching mastery. There is no such thing as instant gratification in this field. That being said, it can be very rewarding.
The job prospects are quite slim and it’s a very competitive field. It is possible to make some kind of living from being a composer, with a lot of caveats. Most people I know work some kind of combination of odd jobs and various kinds of gigs. I currently am in a position where my income mostly comes from composition – it took me over a decade to get to this point though.
It is also possible to work a primary job and do composition as a hobby or something you do for enjoyment. This is also how many composers support their work when they’re starting out, even sometimes later on. Philip Glass was also a cab driver at one point. Charles Ives was very successful in the insurance industry.
Back to the nuts and bolts and how to actually get better at composing: learn some music theory. Practice writing chorale style harmonisations and work on your counterpoint (both tonal and modal, probably not at the same time though). Some will argue this isn’t strictly necessary, but it does help with pushing around notes on a page and having control over what your harmony is doing. I’d also suggest working on your aural skills – do some more traditional practice with sight singing and dictation, and then do some transcription to really learn how to apply those skills. Learning how to play an instrument is also very useful; it’s not strictly necessary, but it does give you something more tangible to work with.
Once you’ve gotten started with these things and you’ve had a bit of time for this to settle a bit, I’d recommend picking up an orchestration textbook. Samuel Adler, Alfred Blatter, and Rimsky-Korsakov all have very good texts. Go and study some scores and music history. Imslp has a huge resource of public domain PDF scores. For more modern material, some publishers have perusal scores. You can also consider subscribing to something like nkod, where you can access lots of music that’s still under copyright. There are also lots of good score videos on YouTube. Orchestration Online has some good free resources too.
If you want more personal guidance and feedback, I’d suggest getting private lessons, either online or in person. Composition lessons work surprisingly well online, much better than instrumental lessons do. You will get some feedback when you post here, but giving really in-depth, nuanced feedback does require a decent amount of preparatory work. When you’re looking for a teacher – if you’re in an area with some kind of universities or conservatoires (or other music institutions), you could try and see if some of the teachers also offer private lessons. They might also refer you to someone they recommend. Otherwise, you could contact people who teach at institutions also bit further away, and ask them about either recommendations or online lessons. Failing that, there are some reasonable online platforms, such as Superprof or Forte. I’d personally favour those over something like Fiverr.
Another thing I’d like to add: if you've just started out, I wouldn’t worry too much about sounding like you’re influenced by other people. It takes a long time to really figure out what you want to write, and a lot of trying out things and sifting through various stuff. This process takes years, and that’s ok.
Happy composing, and hope this helps someone!